Association between Biomarkers of Phthalate Exposure and Serum Folate Concentrations in Children: A Population-Based Cross-Sectional Study of the NHANES from 2011 to 2016.

ABSTRACT

BACKGROUND: Although adverse health effects of phthalates have been reported, very few studies have assessed the associations between biomarkers of phthalate exposure and serum folate concentrations in children. OBJECTIVES: We aimed to examine the association between urinary phthalate metabolites, as biomarkers of exposure to phthalates, and total serum folate concentrations in children using national data from the United States. METHODS: We conducted cross-sectional analyses of 2100 individuals aged 6-18 y enrolled in the National Health and Nutrition Examination Survey, 2011-2016. Multivariable linear regression was applied to examine the relationship between natural logarithm (ln)-transformed urinary phthalate metabolites and serum folate concentrations. The quantile-based g-computation was used to assess the association of urinary phthalate metabolite mixture with serum folate levels. Subgroup analyses were conducted by sex, age, and race/ethnicity, and the interactions were assessed by adding interaction terms of these stratifying variables and phthalates and modeling through the Wald test. RESULTS: In multiple linear regression models, for participants in the highest tertile of MEHHP, MEOHP, DEHP, MCPP, and MCOP, total serum folate concentrations were 1.566 [ß -1.566; 95% confidence interval -2.935, -0.196], 1.423 (-1.423; -2.689, -0.157), 1.309 (-1.309; -2.573, -0.044), 1.530 (-1.530; -2.918, -0.142), and 1.381 (-1.381; -2.641, -0.122) ng/mL lower than those in the lowest tertile. The inverse associations were consistent in different subgroups by sex, age, and race/ethnicity (P for interaction ≥0.083 for all). In addition, the phthalate mixture showed a strong inverse correlation with serum folate; a quartile increase in the phthalate mixture on the ln scale was associated with 0.888 (-0.888; -1.677, -0.099) ng/mL decrease in the serum folate. CONCLUSIONS: Higher concentrations of urinary phthalate metabolites were associated with lower serum folate concentrations in children. Although our findings should be validated through additional population and mechanistic studies, they support a potential adverse effect of phthalate exposure on folate metabolism in children.